interesting, however for the sake of simplicity i'd go with multiple leds, especially spotight, there are not many(more like none), optics you can use with sst\cbt... to get narrow beam, kd sells 90+mm reflectors, but they are quite bulky, i'd go with dozen or more xpe2, there are few small, narrow optics for those leds. i really want to build a spotlight myself, with beam as narrow as hids have, but for now, it is only possible with multiple xpe\xpe2, neither luminus nor mtg2 have such optic available, and i don't want to use big reflector. and even that reflector wont make hid quality beam. aspheric lens is another way, but it is a wow light, not exactly practical.
driving 1 led off 40v battery is not common, for sure. however possible, might not be most efficient way, but doable